And, some stuff has been forgotten. Even if it used to seem pretty important. Speaking about spheres, there's lots of stuff about spherical trigonometry that

And, some stuff has been forgotten. Even if it used to seem pretty important. Speaking about spheres, there's lots of stuff about spherical trigonometry that you can find in old books (say, 1880s to 1920s [1]). They used to think it was math, but it has been determined to not be math any more. It's now stuff that "everyone knows". [1] http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=math;cc=math;rgn=full%20text;idno=00640001;didno=00640001;view=image;seq=9;node=00640001%3A5;page=root;size=100 http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?...